Metallic Material Science


What is Material Tetrahedron? Explain.

The materials science tetrahedron defines the scope of material science and engineering. The tetrahedron emphasize the four interdependent distinct aspect of materials science

·        Processing: The material is synthesized and further made into a component by a set of process methods, such as casting, forming, welding, powder metallurgy etc.

·        Structure: The structure is determined by this process.

·        Properties: The structure in turn determines the properties, which will dictate the performance of the component.

·        Performance: When a certain performance is expected from a component and hence the material constituting the same the expectation is put forth as a set of properties.

 

Lattice parameters of a 2D unit cell?

The lattice parameters of the 2D unit cell are described below.

·        2D lattices can be generated with two basis vectors.

·        They are infinite in two dimensions.

·        There are five distinct 2D lattices

§  Square

§  Rectangle

§  Centered rectangle

§  120o Rhombus

§  Parallelogram

·        Four units cell shapes in 2D can be used for 5 lattices as follows

Square

a=b, α=90

 

Rectangle

a ≠ b, α=90

 

120o Rhombus

a=b, α=120

 

Parallelogram

a ≠ b ≠ α

 

Atonic packing factor of BCC. What is the co-ordination number of BCC?

The body -centered cubic (BCC) unit cell can be imagined as a cube with an atom on each corner and an atom in the cubes center.

So, co-ordination number of BCC is=8

Total number of atoms per unit cell in BCC

 

 

 

Simple cubic

The coordination number of simple cubic crystal is 6

Total number of atoms per unit cell in simple cubic

 




 

 

 

Face centered cubic unit cell

The Face-Centered Cubic (FCC) unit cell can be imagined as a cube with an atom on each corner, and an atom on each face. It is one of the most common structures for metals. 

The coordination number of simple cubic crystal is 12

Total number of atoms per unit cell in FCC

 



What are the types of point defect?

Four types of point of defect are

·        Vacancy

·        Self- interstitials

·        Frenkel defect

·        Impurity atoms

Difference between primitive and non-primitive unit cells?

Primitive unit cell

Non-primitive unit cell

If a unit cell which has effective number of atoms is equal to one.

There is not only one effective number of atom.

Lattice point is present on the corner of the unit cell.

There are additional lattice point either on a face of the unit cell or with in the unit cell.

 

 

Explain 7 crystal system?

There are seven crystal systems.

 

Crystal system

Cell dimensions

Interfacial angles

Cubic

a=b=c

α=β=γ=90

Tetragonal

a=b≠ c

α=β=γ=90

Orthorhombic

a≠ b≠ c

α=β=γ=90

Monoclinic

a≠ b≠ c

α=γ=90∘, β≠90

Triclinic

a≠ b≠ c

α≠β≠γ≠90

Hexagonal

a=b≠ c

α=β=90∘, γ=120

Trigonal or Rhombohedral

a=b=c

α=β=γ≠90